Inertial time delay switch



Feb. 6, 1962 H. F. BARIFFI INERTIAL TIME DELAY SWITCH Filed Oct. 28, 1958 HERBERT F. BARIFFI, INVENTOR AGENT 3,2036? Patented Feb. 6, 1%62 3,020,367 INERTIAL TIME DELAY SWITCH Herbert F. Bariifi, Los Angeles, Calif., assignor to Hughes Aircraft Company, Culver (Iity, Calif, a corporation of Delaware Filed Oct. 28, 1958, Ser. No. 770,228 7 Claims. (Cl. 20061.53)

This invention relates generally to an inertially operated time delay switch mechanism and relates more particularly to a switching device that is operative in response to inertial forces applied thereto.

in the launching of vehicles such as airborne missiles and the like, and particularly vehicles of this type having automatic tracking or guidance systems, it is desirable that initiation of operation of the electrical and electronic apparatus of the guiding mechanism be delayed for a short period of time following release from a parent vehicle. Inasmuch as the parent vehicle may be traveling at various speeds, it is necessary that time delay structures for the purpose described be operable in response to inertial conditions as may be induced by the accelerating force of the missile propellant apparatus. More specifically, it is desirable that the missible be a finite distance from the parent vehicle before initiation of operation of the guidance mechanism. This time delay must be in the order of between 50 and 200 milliseconds.

There are many devices that may be used to secure time delays. Such devices take the form of dash pots, escapement mechanisms, chemical structures such as fuses, and electrical devices such as delay lines and the like. All of these prior structures present some difiiculty in connection with their use in the before-mentioned instance. The desired time delay must be precise and dash pot structures are unreliable as far as the time constants are concerned; escapement mechanisms involve a considerable number of parts with associated high frictional losses; chemical mechanisms do not have an accurately predictable time delay and cannot be protested; and electrical time delay structures often change in character. Of more importance; however, is the fact that all of these prior structures rely upon a fixed time and are not dependent for operation upon inertial factors.

Inertial time delay structures have taken the form of swinging pendulums, passage of fluids such as air or oil through various size orifices and like mechanisms. Free moving apparatus such as pendulums and the like must be relatively large in order to permit use in rapidly accelerating or decelerating structures to provide the desired time delay. Fluid bleed structures involve a considerable number of components and are subject to operational changes in accordance with temperature and pressure variations.

The device of the present invention is a mechanical time delay apparatus that utilizes inertial characteristics of a rotating structure to move an electrical contact member from one position to another. Longitudinal inertial forces are translated into rotary motion with time delay being accurately determined by the inertia of the rotating structure, in the present instance, a flywheel arrangernent.

It is, accordingly, one object of the present invention to provide an inertially operated time delay switch mechanism.

It is another object of the invention to provide a time delay mechanism operable in response to longitudinal acceleration or deceleration thereon.

It is a further object of the invention to provide a time delay mechanism that is simple in construction, reliable and efficient in operation and which includes as few components as possible.

A still further object of the invention is to provide a switch mechanism and acceleration responsive inertially controlled operating means therefor.

Still another object of the invention is to provide an inertial time delay switch structure having lowfrictional characteristics as associated with the operating mechanism and switch contact structures carried by the mechanism.

Another object of the invention is to provide an inertial time delay switch structure that is insensitive to ambient changes in temperature and pressure thereabout.

Other and further important objects of the invention will become apparent from the disclosures in the following detailed specification, appendedclaims and accompanying drawing, wherein:

FIGURE 1 is a top plan view, partially in section, of the inertial time delay switch mechanism of the present invention;

FIG. 2 is a side elevational view of the switch mechanism, partially cut away, and taken substantially as indi cated by line 2-2, FIG. 1; and

FIG. 3 is a transverse sectional view taken substantially as indicated by line 33, FIG. 1.

With specific reference to the drawing, the inertial time delay switch mechanism of this invention is shown as being enclosed within a suitable housing 10. The housing 10 is shown as being unitary; however, in practice, various other arrangements may be used to support and enclose the mechanism of this invention. The housing 10 has a bottom wall 11, side walls 12 and a top wall 13. A pair of pedestals 14 are secured to the bottom wall 11 of the housing 10 as by screws 15. The pedestals 14 are elongated and disposed in spaced parallel relationship adjacent a pair of the side walls 12. Each of the pedestals 14- includes a laterally outwardly disposed rail portion 16 having an elongated slot 17 therein. The pedestals 14 further include a stepdown elongated portion 13 having a gear rack 20 formed thereon, the racks 20 being disposed in parallel relationship to the slots 17.

As shown in the drawing, a shaft 21 is disposed laterally between the pedestals 14, the outer ends of the shaft 21 being fitted with bearings 22 that are disposed within confines of the slots 17. The shaft 21 is further provided, adjacent each end thereof, with gears 23 that are rigidly secured to the shaft and adapted for cooperation with the gear teeth of the racks 20. The gear tooth design of both the racks 20 and the gears 23 is such as to provide a low pressure angle between these teeth and high efficiency separation characteristics therebetween for a purpose to be hereinafter more fully described.

The shaft 21 may preferably be made in two sections and joined together as by a threaded member 24. A bearing 25 is mounted between the shaft sections, the outer race of the bearing 25 serving to support one end of a tension spring 26. The other end of the tension spring 26 is adjustably secured to one of the side walls 12 by means of a suitable fitting 27. The tension spring 26 serves to bias the shaft 21 and components carried thereon in one direction and into contact with one end of the slot 17.

The shaft 21 has a flywheel 28 formed integrally thereon and positioned intermediate the gears 23. The flywheel 23 has a relatively thin web section 30 and has a ring 31 secured to the outer periphery thereof. The ring 31 is preferably made from a heavy material such as lead, tungstem or the like in order to dispose a relatively large amount of heavy material at the periphery of the flywheel 28 and also for a purpose to be hereinafter more fully described.

The shaft 21 further serves to support a contact member indicated generally at 32. The contact member 32 is generally annular and has a central member 33 of an insulating material such as plastic or the like. A metallic ring 34 is secured to the outer periphery of the member 33 and may be swaged thereon and about an annular rib 35 formed from the member 33. fire member 33 has a central opening 36 that is of a diameter slightly larger than the diameter of the shaft 21 and is retained in position on the shaft 21 by means of a pair of spaced snap rings 37. Inner surfaces of the snaprings 3'7 are spaced laterally from lateral surfaces of the member 33 with this lateral spacing cooperating with the annular spacing between the opening 36 and shaft 21 to provide a loose free moving fit between the contact member 32 and the shaft 21. v

Pairs of contacts indicated generally at 40 and 41 are disposed adjacent a pair of opposite sides 12 and laterally with respect to the shaft 21. Each of the pairs of contacts 49 and 41 is supported on a pedestal 42 that is in turn secured to the base portion 11 of the housing by means of suitable screws 43. The contacts 40 and 41 also include contact elements 44 and 45 that have divergent outer end portions that are adapted for cooperation with a peripheral curved surface of the ring 34 of the contact member 32. The contact elements 44 and 45 are connected by means of suitable leads 46 to terminals '47 that are carried by a pair of the sides 12 and accessible from outside of the enclosure 10.

In operation, the time delay mechanism hereof is mounted in a vehicle wherein acceleration of the vehicle will be in the direction of the arrow 50, FIG. 1. When the vehicle carrying the present mechanism is accelerated, inertial forces will move the shaft .21 and elements carried thereby in the direction of the arrow 51 and from the solid line position shown in FIG. 1 to the dotted line position of the components. Prior to such movement, the outer surface of the contact member 32 is biased by means of the spring 26 into contact with the divergent portions of the contact elements 44 and 45 of the contact structure 40. Upon inertial movement of the components, the contact member 32 will be moved into contact with the contact elements 44 and 45 of the contact structure 41. Each of the contact elements 44 and 45 may be suitably connected to guidance structure within the accelerating vehicle, as for example, a latching relay, and serve first to disconnect one portion of the guidance structure and thereafter to connect other portions of the guidance structure. During movement of the mechanism in the direction of the arrow 51, the shaft 21, together with the flywheel 28, will be rotated in the direction of the arrow 52, FIG. 2. During such longitudinal and rotary movement of the shaft 21 and components carried thereby, including the flywheel 28, the shaft 21 is maintained in lateral alignment by means of the gears 23 and racks 20, with the gears 23 being maintained in contact with the racks by disposition of the bearing carrying outer ends of the shaft 21 in the slots 17.

The general time delay available from the device of this invention is determined by the design characteristics of the components, including the length of permitted travel thereof in the direction of the arrow 51, the size, weight and diameter of the flywheel 28 and the ratio between peripheral flywheel weight and total over-all weight of the moving components. A detail adjustment of the time delay is effected by the tension of the spring 26 that may be adjusted through use of the fitting 27. The bearing serves to reduce frictional losses as between one end of the spring 26 and the shaft 21. Actually, the present device has a very small ratio of friction loss to kinetic energy and any variations in the friction coefficient will be very weakly reflected in the time constant of the device. The energy of the moving mass is not absorbed by friction, but rather by impact of the contact member 32 with the contact elements 44 and 45, this action occurring after the desired time delay has been measured. Additionally, rotation of the mechanism about the acceleration axis will produce only a very small yawing torque on the fly- 4 wheel axis. This slight yawing torque will result in only low frictional force between teeth of the gears 23 and the racks 20.

The particular arrangement of the contact member 32 with respect to its mounting on the shaft 21 serves to enable positive contact with both the contact elements 44 and 45. This arrangement also serves to prevent any wedging of the contacting member 32 with respect to the contact elements 44 and 45 and permits easy release of the elements from the contact structure 40.

It may thus be seen that a relatively simple, inertially operated time delay switch mechanism has been provided. The present mechanism is of the utmost simplicity and includes the least number of friction causing elements in order that precise inertially induced time delays may be provided.

Having thus described the invention and the present embodiment thereof, it is desired to emphasize the fact that many modifications may be resorted to in a manner limited only by a just interpretation of the following claims.

I claim:

1. In an inertially operated time delay switch mechanism: a base structure; a rotatable element having an axis and mounted on said base structure for both rotation about said axis and for movement in a direction normal to said axis of said rotation; means carried by said base structure and cooperable with said rotatable element for preventing yawing of said element upon said movement; means disposed between said rotatable element and said base structure for biasing said element against said movement; a contact member carried by said rotatable element; and contact means disposed at least at one end of travel of said element.

2. In an inertially operated time delay switch mechanism: a base structure; a rotatable shaft element having an axisand including a flywheel mounted on said base structure for both rotation about said axis and for movement in a direction normal to said axis of saidrotation; means carried by said base structure and cooperable with said shaft element for preventingyawing of said element upon said movement; means disposed between said shaft element and said base structure for biasing said element against said movement; a contact member carried by said shaft element; and contact means disposed at least at one end of travel of said element.

3. An inertially operated time delay switch mechanism comprising: a base structure; a rotatable shaft element having an axis and mounted on said base structure for both rotation about said axis andfor movement in a direction normal to said axis of said rotation; a flywheel carried by said shaft element; means carried by said base structure and cooperable with said shaft element for preventing yawing of said element upon said movement;

tension spring means disposed between said shaft element and said base structure for biasing said element against said movement; a contact member freely carried by said shaft element; and contact means disposed at least at one end of travel of said element.

4. An inertially operated time delay switch mechanism comprising, in combination: a base structure; a rotatable shaft element having an axis and mounted on said base structure for both rotation about said axis and for movement in a direction normal to said axis of said rotation; a peripherally weighted flywheel carried by acentral area of said shaft element; elongated rack means carried by said base structure and cooperable with gears carried by said shaft element for preventing yawing of said element upon said movement; adjustable tension spring means dis posed between said shaft element and said base structure for biasing said element against'said movement; a contact member freely carried by said shaft element; and Contact means disposed at least at one end of travel of said element.

5. An inertially operated time delay switch mechanism comprising: a base structure; a pair of spaced pedestals secured to said base structure and having elongated slots therein; a shaft disposed between said pedestals and havend portions disposed in said slots; at flywheel carried by said shaft and disposed intermediate said pedestals; a gear rack carried by each of said pedestals; gear means carried by said shaft adjacent said end portions thereof, said gear means being operatively associated with said racks; spring means disposed between said shaft and said base structure for biasing said shaft and said flywheel carried thereby toward one end of travel of said shaft within limits of said slots; a contact member carried by said shaft; and at least one pair of contacts disposed at at least one limit of travel of said shaft, said contacts being carried by said base structure and adapted for cooperation with said contact member, said shaft, flywheel and contact member being adapted for both rotational and for lateral movement in a direction normal to an axis of rotation upon application of inertial forces thereto, whereby to move said contact member between said pairs of contacts in a finite time.

6, An inertially operated time delay switch mechanism comprising, in combination: a base structure; a pair of spaced pedestals secured to said base structure and having elongated slots therein; a shaft disposed between said pedestals and having outer end portions disposed in said slots; a flywheel carried by said shaft and disposed intermediate said pedestals; a gear rack carried by each of said pedestals; gear means carried by said shaft adjacent said end portions thereof, said gear means being operatively associated with said racks; spring means disposed between said shaft and said base structure for biasing said shaft and said flywheel carried thereby toward one end of travel of said shaft within limits of said slots; a freely movable contact member carried by and electrically insulated from said shaft; and pairs of contacts disposed at limits of travel of said shaft, said contacts being carried by said base structure and adapted for cooperation with said contact member, said shaft, flywheel and contact member being adapted for both rotation and for lateral movement in a direction normal to an axis of rotation upon application of inertial forces thereto, whereby to move said contact member between said pairs of contacts in a finite time.

7. An inertially operated time delay switch mechanism comprising, in combination: a base structure; a pair of spaced pedestals secured to said base structure and having elongated slots therein; a shaft disposed between said pedestals and having outer end portions disposed in said slots; bearing means carried by said end portions of said shaft and engageable with surfaces of saidslots; a peripherally weighted flywheel carried by said shaft and disposed intermediate said pedestals; a gear rack carried by each of said pedestals; gear means carried by said shaft adjacent said end portions thereof, said gear means being operatively associated with said racks; adjustable tension spring means disposed between said shaft and said base structure for biasing said shaft and said flywheel carried thereby toward one end of travel of said shaft within limits of said slots; a freely movable contact member carried by and electrically insulated from said shaft; and pairs of divergent contacts disposed at limits of travel of said shaft, said contacts being carried by said base structure and adapted for cooperation with said contact member, said shaft, flywheel and contact member being adapted for both rotation and for lateral movement in a direction normal to an axis of rotation upon application of inertial forces thereto, whereby to move said contact member between said pairs of contacts in a finite time.

References Cited in the file of this patent UNITED STATES PATENTS 2,496,310 Rabinow Feb. 7, 1950 2,583,202 Benson Jan. 22, 1952 2,733,116 Fanthan et al. Jan. 31, 1956 2,836,118 Hjelm May 27, 1958 2,868,916 Neuworth et al. Jan. 13, 1959 2,882,826 Billings Apr. 21, 1959 

